<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <button>点击</button>
    <div></div>
    <script>
        var btn = document.querySelector('button');
        var div = document.querySelector('div');
        var time = 5;
        btn.addEventListener('click', function () {
            // console.log(location.href)
            location.href = 'http://www.itcast.cn'
        })
        div.innerHTML = time;
        setInterval(function () {
            div.innerHTML = --time;
            if (time == 0) {
                location.href = 'http://www.baidu.com'
            }
        }, 1000)
    </script>
</body>

</html>